Regulation of prostaglandin receptors in myocardial ischemia.

Sarcolemmal membranes from pig hearts express a homogenous class of binding sites for [3H]PGE1. Competition binding studies with EP receptor suptype selective ligands suggest an EP3 receptor subtype. The GTP analogue GTP gamma S reduced affinity without changing binding capacity, indicating a G protein coupled EP3 receptor. Regional myocardial ischemia (60 min) in anesthetized, open-chest pigs caused a 50% increase of the number of binding sites while GTP gamma S still decreased [3H]PGE1 binding, suggesting intact G protein coupling. Myocardial ischemia may, therefore, modify myocardial actions of prostaglandins.